In the field of radio communications, a receiver apparatus performs channel estimation to learn a radio channel state. Since the receiver apparatus performs demodulation and decoding using channel estimation results, transmission performances are greatly degraded if the accuracy of the channel estimation is decreased. To perform accurate channel estimation, statistic property of a channel needs to be identified. The statistic property of the channel includes power of a path forming a channel, and a delay time from a previously received path. FIG. 1 illustrates an example of a channel impulse response of a channel in the time domain, and arrows labeled 100-1 through 100-8 denote paths. Labels 100-4 and 100-5 are intended to mean delay times where no significant paths are present. Such a location is herein interpreted as a path having zero power.
Non Patent Literature 1 describes a method of estimating all paths from a preceding path to a path having a predetermined delay time in channel estimation of scattered pilot OFDM. In the example of FIG. 1, paths 100-1 through 100-8 are estimated.